Check is_missing_host_keys before adding them

main.py

@@ -40,8 +40,19 @@ class AutoAddPolicy(paramiko.client.MissingHostKeyPolicy):
     """
     lock = threading.Lock()
 
+    def is_missing_host_keys(self, client, hostname, key):
+        k = client._host_keys.lookup(hostname)
+        if k is None:
+            return True
+        host_key = k.get(key.get_name(), None)
+        if host_key is None:
+            return True
+        if host_key != key:
+            raise paramiko.BadHostKeyException(hostname, key, host_key)
+
     def missing_host_key(self, client, hostname, key):
         with self.lock:
+            if self.is_missing_host_keys(client, hostname, key):
                 keytype = key.get_name()
                 logging.info(
                     'Adding {} host key for {}'.format(keytype, hostname)